Aqueous Chloride Research Articles

In Silico Drug Design of Benzothiadiazine Derivatives Interacting with Phospholipid Cell Membranes.

The use of drugs derived from benzothiadiazine, a bicyclic heterocyclic benzene derivative, has become a widespread treatment for diseases such as hypertension, low blood sugar or the human immunodeficiency virus, among others. In this work we have investigated the interactions of benzothiadiazine and four of its derivatives designed in silico with model zwitterionic cell membranes formed by dioleoylphosphatidylcholine, 1,2-dioleoyl-sn-glycero-3-phosphoserine and cholesterol at the liquid–crystal phase inside aqueous potassium chloride solution. We have elucidated the local structure of benzothiadiazine by means of microsecond molecular dynamics simulations of systems including a benzothiadiazine molecule or one of its derivatives. Such derivatives were obtained by the substitution of a single hydrogen site of benzothiadiazine by two different classes of chemical groups, one of them electron-donating groups (methyl and ethyl) and another one by electron-accepting groups (fluorine and trifluoromethyl). Our data have revealed that benzothiadiazine derivatives have a strong affinity to stay at the cell membrane interface although their solvation characteristics can vary significantly—they can be fully solvated by water in short periods of time or continuously attached to specific lipid sites during intervals of 10–70 ns. Furthermore, benzothiadiazines are able to bind lipids and cholesterol chains by means of single and double hydrogen-bonds of characteristic lengths between 1.6 and 2.1 Å.

First Report of Cladosporium tenuissimum Causing Leaf Spots on Carnation in China.

Carnation (Dianthus caryophyllus L., Caryophyllaceae) is a popular and important market flower in China (Kayamori et al., 2012). Leaf spots of Cladosporium tenuissimum Cooke were first observed in early October 2016 on carnation grown on the academy of agricultural sciences as well as in parks in Xi'an city (108°54'18.6696"E, 34°15'12.9"N), with nearly 80% of leaves on individual plants infected. Carnation in five nearby parks were surveyed with 60 to 100% disease incidence. Initially, the symptoms appeared as small dark elliptical necrotic lesions surrounded by a dark brown halo. Some leaf spots in severe cases covered the entire leaf surface. Necrotic tissue was treated with lactophenol and used for microscopic examination. Sporulation was seen on the necrotic tissue. To identify the pathogen, eighteen leaf pieces (3-5 mm) with both infected and healthy portions were taken at the edge of lesions and surface-disinfected by placing them in 75% ethanol for 5 s, then transferred to a 0.1% aqueous mercuric chloride solution for 30 s and rinsed with sterilized water three times. Six sections were placed on each potato dextrose agar (PDA) at 25°C in the dark. Ten pure fungal cultures were obtained from single spores. Colonies on PDA were greyish to dark brown and showed a velvety texture. Subcylindrical to subclavate conidiophores were solitary or in loose groups, on leaves and stems erumpent through the cuticle or emerging through stomata, and measured 49-513 × 3-7 µm (n=50). Ramoconidia were subcylindrical, 15-31 × 4-5 µm, aseptate, basal hilum 2-3.5 µm diam. Morphological characteristics of the pathogen were similar to Cladosporium tenuissimum Cooke (Bensch 2010). For molecular identification, pure cultures of ten single-spore isolates were extracted from mycelium using the Plant Genomic DNA Kit (TIANGEN, China). Three different genomic DNA regions-ribosomal DNA internal transcribed spacer (ITS) region, partial translation elongation factor-1 alpha (EF), and actin (ACT) were amplified using the primers ITS1/ITS4 (White et al. 1990), ACT-512F/ACT-783R (Carbone and Kohn 1999), and EF1-728F/EF1-986R (Carbone and Kohn 1999), respectively. Phylogenetic analysis of multiple genes was conducted with the neighbor-joining method using MEGA 7 (Bakhshi et al. 2018). The sequences of our isolate (CTK) and seven published sequences of C. tenuissimum were clustered into one clade with a 100% bootstrap supporting level. The sequences of CTK have been deposited in GenBank with accessions MZ351731 for ITS, MZ351730 for ACT, MZ351732 for TEF1. Isolate pathogenicity was tested on surface disinfested leaves of two-month-old carnation plants by spraying a 2 × 106 conidial per ml at 25°C incubation temperature. Another set of plants was sprayed with sterile water as non-inoculated controls. Three replicates of every isolate were conducted, and each replicate included 5 carnation plants. After twelve days, only the inoculated leaves showed leaf blight resembling those observed on naturally infected carnation leaves. The pathogen was consistently reisolated from the infected leaves with the aim of completing Koch's postulates. To our knowledge, this is the first report of C. tenuissimum causing carnation leaf spots in China and worldwide. Thus, the identification of C. tenuissimum for this disease is important for the advancement of effective prevention and control approaches as future prospects.

Self-Propelled Motion of an Oil Droplet Containing a Phospholipid and its Stability in Collectivity

Collective cell migration (CCM) is a universal process that is responsible for various biological phenomena in living organisms. Therefore, unraveling the mechanism of CCM is critical for understanding the principles underlying such processes and for their application in biomaterials and biomedical science. Among these phenomena, unjamming/jamming transitions are particularly intriguing as they are controlled by three factors: cell motility, cell density, and cell–cell adhesion. However, there is no experimental system to independently demonstrate and control these effects. In this study, we added 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) to a nitrobenzene droplet containing KI and I2 to develop a prototype system that shows self-propelled motion in an aqueous trimethylstearylammonium chloride (TSAC) solution. First, we explored the relationship between the motility of the droplet and experimental parameters, namely, the concentrations of TSAC, I2, and DMPC and droplet size. The droplet showed directional motion driven by Marangoni convection owing to a solubilization promoted by the formation of mixed micelles filled with oil between DMPC and TSA+; notably, droplet motility could be controlled by each parameter. Furthermore, the interfacial tension (γ) at the oil–water interface, measured using the pendant drop method, indicated that each parameter contributed to changes in γ. Based on our experimental results, we inferred that the dynamics of the insertion of TSA+ in the aqueous phase into the self-assembled DMPC membrane covering the nitrobenzene droplet, as well as the solubilization, are important factors that trigger Marangoni convection and lead to controlled droplet motility. Furthermore, the developed droplets remained stable in a confluent state, wherein they were in contact with each other and exhibited various polygonal shapes depending on their size and density because they were protected by a robust self-assembled DMPC membrane layer. The results indicated that the density and the morphology of the droplets are controllable in this system, and that they indirectly altered droplet adhesion. Thus, we procured a prototype system that could be controlled independently using three parameters to elucidate phase transition for CCM. This system can be biomodified through the combination of phospholipids with any biomolecule and can enable a more precise evaluation of the CCM exhibited by living cells.

Leaded or unleaded? Homemade microscale tin electroplating

Abstract Social distancing measures due to the SARS-CoV-2 virus have profoundly challenged the educational experimental work. We have sought to remediate this issue by designing a series of low cost, low risk, quick, and qualitative electrochemistry and corrosion experiments to be performed in the student’s homes at the microscale with a kit provided by the teacher. One such experience is the electroplating of Sn from an aqueous chloride solution using readily available soldering wires (e.g., Sn–Pb alloy, or Sn–Ag–Cu alloy). This process catches students’ attention due to its simplicity and variety of possible applications that include corrosion protection, fabrication of electronic components, plating of cooking utensils, lithium batteries, etc.

Ion Coordination in Aqueous Lanthanum Chloride and Lanthanum Nitrate Solutions as Probed by X-ray Diffraction

Ion Coordination in Aqueous Lanthanum Chloride and Lanthanum Nitrate Solutions as Probed by X-ray Diffraction

The Role of Micro Pits in the Initiation Process of Crevice Corrosion of SUS304 Stainless Steel in an Aqueous Chloride Solution

The Role of Micro Pits in the Initiation Process of Crevice Corrosion of SUS304 Stainless Steel in an Aqueous Chloride Solution

Interaction behavior of sucrose in aqueous tributylmethylammonium chloride solutions at various temperatures: A volumetric, ultrasonic and viscometric study

Physical properties such as density (ρ), sound speed (u) and viscosity (η) for varied compositions of a saccharide (sucrose) in water and mixed aqueous tributylmethylammonium chloride solvent media has been scrutinised at five discrete temperatures ranging (293.15 K - 313.15 K) and under ambient pressure (101.3 kPa). The empirically procured data has been employed to enumerate different volumetric, acoustic and viscometric parameters like apparent molar parameters (Kϕ,s, Vϕ), partial molar parameters (K0ϕ,s, V0ϕ), transfer parameters (K0ϕ,s,tr, V0ϕ,tr, Btr), hydration number, pair and triplet interaction coefficients, solvation number, viscosity B-coefficient etc. The temperature derivative of viscosity B-coefficient i.e. dB/dT values have been utilized to examine structure making ability of the solute. Also, Gibbs free energy of activation for both solute and solvent has been determined and the influence of temperature on the solute-solvent interactions has been addressed. Moreover, the co-sphere overlap model has been employed for better comprehension of various prevalent intermolecular interactions in the considered systems.

Microencapsulation of camphor using trimethylsilylcellulose

Microencapsulation of camphor by trimethylsilylcellulose was performed using oil-in-water emulsion method. Trimethylsilylcellulose (TMSC) with the DS value of 2.41 (CHN analysis) was synthesized by dissolving commercial cellulose in N, N-dimethylacetamide/LiCl followed by reacting with hexamethyldisilazane. Sodium dodecyl sulfate (SDS) in acidic aqueous solution and tetramethylammonium chloride (TMACl) in water were attempted as emulsifiers. The oil phase composed of TMSC and camphor in ethyl acetate was dispersed in emulsifier solution. The mass ratio of TMSC to camphor and emulsifier concentration were optimized to produce high quality microcapsules. Using the mass ratio of 3:7 and 1% (w/v) SDS solution gave well separated microcapsules of TMSC_C_SDS (1). The diameter size in the micron range (10–110 mm) and high camphor content (∼21.07%) were obtained from this sample. The larger size of the capsules obtained from TMACl system indicated the coalescence of the oil droplets. The hydrolysis of the external surface of the microcapsules was observed in the SDS system. However, this caused a minor effect on the cellulose stability in TMSC_C_SDS (1). The freshly prepared microcapsules of TMSC_C_SDS (1) showed the fast release of camphor during first 2 h and reached the equilibrium after 7 h.

Subsistence of diverse interactions of some biologically important molecules in aqueous ionic liquid solutions at various temperatures by experimental and theoretical investigation

To investigate significant molecular interactions, different Physico-chemical methodologies have been studied and measured for mixtures of aqueous Benzyltriethylammonium chloride with two amino acids (L-Cysteine and Glycine) at various concentrations and temperatures under atmospheric pressure. The origin of various interactions is exposed by evaluating the apparent molar volume (ϕV), limiting apparent molar volume (ϕV0), viscosity A and Bcoefficients, molar refraction (RM), limiting molar refraction (RM0), and detected strong solute-solvent interaction is predominating over the solute-solute and also solvent-solvent interactions in the ternary mixtures. The solute-solvent interaction is measured through (δϕE0/δT)P and (dB/dT) data which provide information like structure-breaking. The findings of 1H NMR spectroscopy show that, in addition to H-bonding interactions, the ionic liquid and amino acids have significant hydrophobic-hydrophobic interactions, which is confirmed by theoretical explanations. L-Cysteine-IL interactions are more prominent than Glycine-IL interactions, according to both experiment and theory.

Influence of aqueous chloride and bromide ions on bisphenol A degradation efficiency with zinc oxide nanoparticles

Zinc oxide (ZnO) nanoparticles (NPs) have been widely investigated for applications in photocatalytic degradation of organic pollutants in wastewater. Despite the advantages of robust ZnO material, its photocatalytic activity is greatly affected by environmental factors. Halogen ions are commonly found in wastewater, which directly affect the pollutant aggregation and sedimentation, therefore it is necessary to discuss their effect on the photocatalytic degradation. The current study assesses the halogen ions effect on the photocatalytic degradation of bisphenol A (BPA) using different dosage of sodium chloride (NaCl) and sodium bromide (NaBr). The microstructural characterization of ZnO NPs was conducted by transmission electron microscopy and hydrodynamic size was analyzed through dynamic light scattering. The effective BPA degradation with ZnO NPs was observed and pseudo-first-order kinetics was calculated. The increase of ZnO NPs dosage from 10 to 100 mg L− 1 enhanced the degradation rate constant of BPA up to 0.089 min− 1 (14.8 folds). In order to evaluate the role halogen ions to degrade BPA, NaBr and NaCl were used. The degradation rate was reduced to 0.0034 min− 1 after the addition of NaBr due to the increase in hydrodynamic particle size, thereby restricting the light adsorption capacity. Noteworthy, upon addition of NaCl up to 500 mM concentration, only a slight decrease on BPA degradation rate was observed. Therefore, this study unveils the role of chloride ions as an effective medium for BPA degradation by ZnO NPs, without aggregation, and provides a novel platform for the treatment of organic pollutants in saline water.

Safe, accurate, and precise sulfur isotope analyses of arsenides, sulfarsenides, and arsenic and mercury sulfides by conversion to barium sulfate before EA/IRMS

The stable isotope ratios of sulfur (δ34S relative to Vienna Cañon Diablo Troilite) in sulfates and sulfides determined by elemental analysis and isotope ratio mass spectrometry (EA/IRMS) have been proven to be a remarkable tool for studies of the (bio)geochemical sulfur cycles in modern and ancient environments. However, the use of EA/IRMS to measure δ34S in arsenides and sulfarsenides may not be straightforward. This difficulty can lead to potential health and environmental hazards in the workplace and analytical problems such as instrument contamination, memory effects, and a non-matrix-matched standardization of δ34S measurements with suitable reference materials. To overcome these practical and analytical challenges, we developed a procedure for sulfur isotope analysis of arsenides, which can also be safely used for EA/IRMS analysis of arsenic sulfides (i.e., realgar, orpiment, arsenopyrite, and arsenian pyrite), and mercury sulfides (cinnabar). The sulfur dioxide produced from off-line EA combustion was trapped in an aqueous barium chloride solution in a leak-free system and precipitated as barium sulfate after quantitative oxidation of hydrogen sulfite by hydrogen peroxide. The derived barium sulfate was analyzed by conventional EA/IRMS, which bracketed the δ34S values of the samples with three international sulfate reference materials. The protocol (BaSO4-EA/IRMS) was validated by analyses of reference materials and laboratory standards of sulfate and sulfides and achieved accuracy and precision comparable with those of direct EA/IRMS. The δ34S values determined by BaSO4-EA/IRMS in sulfides (arsenopyrite, arsenic, and mercury sulfides) samples from different origins were comparable to those obtained by EA/IRMS, and no sulfur isotope fractionations were introduced during sample preparation. We report the first sulfur isotope data of arsenides obtained by BaSO4-EA/IRMS.Graphical abstract

Honey bee (Apis mellifera ligustica) acetylcholinesterase enzyme activity and aversive conditioning following aluminum trichloride exposure

BackgroundAluminum is the third most prevalent element in the earth’s crust. In most conditions, it is tightly bound to form inaccessible compounds, however in low soil pH, the ionized form of aluminum can be taken up by plant roots and distributed throughout the plant tissue. Following this uptake, nectar and pollen concentrations in low soil pH regions can reach nearly 300 mg/kg. Inhibition of acetylcholinesterase (AChE) has been demonstrated following aluminum exposure in mammal and aquatic invertebrate species. In honey bees, behaviors consistent with AChE inhibition have been previously recorded; however, the physiological mechanism has not been tested, nor has aversive conditioning.ResultsThis article presents results of ingested aqueous aluminum chloride exposure on AChE as well as acute exposure effects on aversive conditioning in an Apis mellifera ligustica hive. Contrary to previous findings, AChE activity significantly increased as compared to controls following exposure to 300 mg/L Al3+. In aversive conditioning studies, using an automated shuttlebox, there were time and dose-dependent effects on learning and reduced movement following 75 and 300 mg/L exposures.ConclusionsThese findings, in comparison to previous studies, suggest that aluminum toxicity in honey bees may depend on exposure period, subspecies, and study metrics. Further studies are encouraged at the moderate-high exposure concentrations as there may be multiple variables that affect toxicity which should be teased apart further.

Analysing the molecular interactions of ternary (lactose + water + tributylmethylammonium chloride) solutions at different temperatures via physicochemical methods

The interactions of lactose with tributylmethylammonium chloride (Bu3MeNCl) as the function of temperature have been studied by amalgamation of volumetric, acoustic and viscometric methods. Density, ultrasonic speed, and viscosity for varying concentrations of lactose in water and in (0.020, 0.039, 0.059, 0.079) mol.kg−1 aqueous solutions of Bu3MeNCl have been determined at five distinct temperatures (T = 293.15–313.15) K. These experimental values have been used to calculate apparent molar volume, Vϕ, limiting apparent molar volume, V0ϕ, apparent molar isentropic compression, Kϕ,s, limiting apparent molar isentropic compression, K0ϕ,s, viscosity B-coefficient, their transfer values, pair and triplet interaction coefficients, and hydration number nH. The Gibbs free energy of activation for solvent (Δµ01#) and Gibbs free energy of activation for lactose (Δµ02#) in water and in aqueous solutions of Bu3MeNCl have also been assessed and the obtained results support the outcome of volumetric, acoustic and viscometric parameters. These parameters provide better understanding of molecular interactions like solute-solute, solute-solvent interactions present in the systems. Further, it helps in determining structural and functional properties of studied systems and acquired results revealed that the solutions are characterized predominantly by solute-solvent interactions. Also, the values of second derivative of limiting apparent molar volume with respect to temperature indicated that the lactose monohydrate behaves as a structure maker in aqueous tributylmethylammonium chloride solutions.

Hydrodynamic slip of alkali chloride solutions in uncharged graphene nanochannels.

Using non-equilibrium molecular dynamics simulations, we demonstrate the effect of concentration and alkali cation types (K+, Na+, and Li+) on the hydrodynamic slip of aqueous alkali chloride solutions in an uncharged graphene nanochannel. We modeled the graphene-electrolyte interactions using the potential of Williams et al. [J. Phys. Chem. Lett. 8, 703 (2017)], which uses optimized graphene-ion Lennard-Jones interaction parameters to effectively account for surface and solvent polarizability effects on the adsorption of ions in an aqueous solution to a graphene surface. In our study, the hydrodynamic slip exhibits a decreasing trend for alkali chloride solutions with increasing salt concentration. The NaCl solution shows the highest reduction in the slip length followed by KCl and LiCl solutions, and the reduction in the slip length is very much dependent on the salt type. We also compared the slip length with that calculated using a standard unoptimized interatomic potential obtained from the Lorentz-Berthelot mixing rule for the ion-carbon interactions, which is not adjusted to account for the surface and solvent polarizability at the graphene surface. In contrast to the optimized model, the slip length of alkali chloride solutions in the unoptimized model shows only a nominal change with salt concentration and is also independent of the nature of salts. Our study shows that adoption of the computationally inexpensive optimized potential of Williams et al. for the graphene-ion interactions has a significant influence on the calculation of slip lengths for electrolyte solutions in graphene-based nanofluidic devices.

Concentration dependent electrochemical performance of aqueous choline chloride electrolyte

In this work we have analysed the performance of aqueous choline chloride as an electrolyte in supercapacitors. The aqueous choline chloride electrolyte is prepared in molar concentrations of 0.3, 0.5, 0.7, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 and 4. The different concentrations of aqueous choline chloride electrolyte are used to fabricate activated carbon electrode based supercapacitors. The prepared electrolytes are characterized using FTIR technique and their ionic conductivity and electrochemical stability window are analysed using electrochemical impedance spectroscopy and cyclic voltammetry respectively. The electrochemical stability window is found 1.8 V for all concentration of choline chloride electrolytes. The highest conductivity is 129 mS/cm for 2.5 M aqueous choline chloride and two peaks feature is observed in ionic conductivity vs. concentration of electrolyte plot. The electrochemical performance of supercapacitors is analysed using cyclic voltammetry and electrochemical impedance spectroscopy, the supercapacitors showed good charge propagation and highest specific capacitance is reported for 1.0 M electrolyte (5.75F/g).

Treatment of Excision Wound of Melanoma In Situ of the Trunk and Extremities with Zinc Chloride Solution

The majority of physicians treating melanoma in situ recommend a 5mm to 1cm margin with excision into the subcutaneous tissue extending between the superficial and the deep fat. There is always the potential for an unrecognized invasive component in a melanoma in situ, making aqueous zinc chloride solution an ideal agent to treat the excision wound of a melanoma in situ of the trunk and extremities. Zinc chloride solution penetrates deeply and widely, killing and fixing tissue when applied to the excision wound, facilitating the excision by allowing for a simple saucerized excision with a narrower and thinner margin while ensuring the treatment of any possible unrecognized invasive components. Zinc chloride has been used in a paste since 1835 to treat skin cancers and melanoma but unlike pastes zinc chloride in solution is recognized by the U.S. Food & Drug Administration as a generally safe substance (Code of Federal Regulations Title 21 [Part 182]). The solution penetrates as deeply and widely and effectively as in the paste which Mohs described to be an inactive vehicle for the active ingredient, zinc chloride solution. Mohs reported a large significant survival benefit (p=0.003) for invasive melanoma using surgery combined with zinc chloride over conventional melanoma surgery. Zinc chloride solution without the paste is a new medicine effective as a surgical adjuvant in the treatment of the excision wound of a melanoma in situ of the trunk and extremities. Zinc chloride can be used as a surgical adjuvant for any melanoma, but melanoma in situ of the trunk and extremities is the logical starting point for a physician interested in using this adjuvant in the treatment of melanoma. Zinc chloride is very powerful and potentially scarring and should be used on the excision wound of a previously histologically diagnosed melanoma only.

A new approach to investigate the ionic conductivity of NaCl and KCl solutions via impedance spectroscopy

Lima et al. [1] employed electrical impedance spectroscopy to analyze the electrical impedance behavior of dilute aqueous potassium chloride (KCl) and sodium chloride solutions in the frequency range of 10−1 Hz to 106 Hz (NaCl). The complex impedance Z* data from the solutions were modeled using an analogous electrical circuit that closely matched the experimental data. The electrical characteristics of the solutions were studied as a function of the cation types. The Debye model accurately describes the bulk effects of K+ and Na+ cations. However, it appeared that the analysis presented just the equivalent circuit components as a function of salt concentration. As a result, the current work used a simulation procedure to generate complex impedance (Z*) data from electrical parameters derived from the analogous circuit. To highlight the high-frequency relaxation processes occurring, extrapolation to a broader frequency range was performed. Furthermore, theoretical considerations were introduced in order to derive complex conductivity (σ*) from complex admittance (Y*). In the complex impedance (Z*) and admittance (Y*), there was a good correlation between all parameters derived from both processes. The key relaxation process characteristics, such as ionic strength, relaxation time, and conductivity values at low and high frequencies, were then retrieved. As a function of salt concentration, all of these parameters were evaluated and discussed.

Green Synthesis of Gold Nanoparticles: A Novel, Environment-Friendly, Economic, Safe Approach

Nanoparticles can be synthesised using a variety of methods. These approaches, on the other hand, are connected with the development of undesired byproducts that are both harmful and expensive. As a result, several attempts are being undertaken to develop unique, cost-effective, safe, and dependable "green" techniques for producing desirable nanoparticles. To develop a novel, environment-friendly, economic, safe approach to the synthesis of gold nanoparticles via the biological entity. Addition of aqueous gold chloride solution to the microwave-exposed aqueous extracellular Cassia tora leaf extract yielded poly shaped gold nanoparticles. The UV-vis. spectroscopic investigations are led to notice and affirm the formation of nanoparticles. FTIR studies are performed to affirm the role of a biomolecule in stabilizing the nanoparticles. X-beam diffraction study is utilized to affirm the crystalline nature of nanoparticles. The elemental characterization of the samples is regulated by EDX studies. The size and morphology of the synthesized nanoparticles are explored using HR-TEM analysis and FESEM. It is seen that the flavonoids which are separated during microwave warming of extracellular solution of the cassia tora leaves are liable for the biosynthesis of gold nanoparticles. The nanoparticle was noted to be well dispersed and polyshaped with a 20-60 nm range. The leaf extract based preparation of AuNP is more gainful since leaf is used instead of microorganism as many of the issues like pathogenicity, procedural maintenance of hygiene of cell culture and labor efforts can be overcome. The presence of flavonoids in the leaf was discovered by the examination of produced nanoparticles, suggesting that they may have fulfilled both reduction and stabilisation activities. The presented approach can be inferred to be cost-effective, environmentally friendly, and capable of manufacturing nanoparticles with desired physical and pharmacological properties.

Bovine bone-derived natural hydroxyapatite-supported ZnCl2 as a sustainable high efficiency heterogeneous biocatalyst for synthesizing amidoalkyl naphthols

Waste-derived materials have emerged as promising catalysts to meet the requirements for green chemistry. Catalysts and solvents are recognized as the most important components of the 12 principles of green chemistry. The reactivity of members of this class of materials can be increased by loading them with metal salts. Thus, in the present study, we loaded waste bovine bone-derived hydroxyapatite (BBHA) with 10−2 mol L−1 aqueous zinc chloride (ZnCl2) solution and used it as a catalyst for synthesizing 1-amidoalkyl-2-naphthols derivatives in a solvent-free, one-pot, three-component condensation method with 2-naphthol, aldehydes, and either urea or acetamides at a reaction temperature of 80 °C. First, we extracted natural hydroxyapatite from waste bovine bone by thermal decomposition at 800 °C for 2 h. The hydroxyapatite was then loaded with ZnCl2 and its physical and chemical characteristics were assessed. Second, the reaction conditions were optimized in terms of the catalyst loading, solvent, and reaction temperature. Under the optimal reaction conditions, the desired compounds were obtained with high yields (86%–96%) in only 25–40 min using a small amount of catalyst (50 mg). This proof-of-concept study demonstrates the potential use of a waste bone-derived natural hydroxyapatite-supported ZnCl2 catalyst with high yields and sustainability.

Solvometallurgical Process for the Recovery of Tungsten from Scheelite

The industrial state-of-the-art processes to extract tungsten from scheelite (CaWO4) require high pressures and temperatures. These flowsheets consume a large excess of chemicals (which are very hard to recycle) and generate up to 25 tons of high-salinity wastewater per ton of ammonium paratungstate product. In this work, a more sustainable conceptual flowsheet for the recovery of tungsten from high-grade (55.0 wt % W) and medium-grade (3.3 wt % W) scheelite ores was developed at the lab scale. Leaching of CaWO4 was tested in solutions of 37.0 wt % aqueous HCl in organic solvents (ethylene glycol, poly(ethylene glycol) 200, acetonitrile) and ionic liquids (Aliquat 336). The tungstate (HxWyOzn–) generated by the reaction between CaWO4 and HCl was only solubilized in the ethylene glycol system with an appropriate amount of 37.0 wt % aqueous HCl, whereas in all other solvents, it either precipitated or CaWO4 did not dissolve. After the dissolution of tungsten, nonaqueous solvent extraction was used to separate tungsten from calcium, by means of a solvent consisting of 20 vol % Aliquat 336 in the aliphatic diluent GS190 with 10 vol % 1-decanol as a modifier. Scrubbing with water removed the co-extracted iron. Finally, tungsten was recovered as ammonium tungstate (NH4)2WO4, the precursor of ammonium paratungstate, by stripping in a mixture of aqueous ammonia and ammonium chloride. Paratungstate is the most common intermediate for the production of tungsten oxide or tungsten metal. One drawback that needs to be adequately addressed, prior to further upscaling of this conceptual flowsheet, is the potential formation of trace levels of 2-chloroethanol in the leaching stage. It is hypothesized that this problem can be circumvented by further optimizing process conditions to enhance the mass transfer and reduce the reaction time, such as better mixing of the solid and the lixiviant.